Apparatus and method for processing heat reactive thermoplastic tubing and the product formed thereby

ABSTRACT

An apparatus for processing flattened heat-reactive thermoplastic tubing to provide a bulge along at least one, and preferably both, lateral edges to facilitate entry of an object into the tubing to expand the full width of the tubing and facilitate the packaging of an object therewithin. The apparatus advances the flattened tubing past a source of heat so related to the edge or edges to be bulged as to soften only these edge portions of the tubing thereby relieving internal stresses therein and allowing the same to bulge and take a set in bulged condition as it cools.

United States Patent 1191 Plummer 1451 Apr. 23, 1974 [54] APPARATUS AND METHOD FOR 3,530,538 9/1970 Quackenbush 425/384 PROCESSING HEAT REACTIVE 3,576,051 4/1971 Click 425/72 3,574,804 4/1971 Joonase 425/384 THERMOPLASTIC TUBING AND THE PRODUCT FORMED THEREBY Inventor: Walter A. Plummer, 3546 Crownridge Dr., Sherman Oaks, Calif. 91403 Filed: Apr. 29, 1971 Appl. No.: 138,441

Related US. Application Data Division of Ser. No. 824,102, May 13, 1969f abandoned.

US. Cl. 425/383, 425/66 Int. Cl ..-B29f 5/00 Field of Search 264/95; 425/66, 383, 384

References Cited UNITED STATES PATENTS 9/1967 Barnhart 264/95 Primary Examiner-Richard B. Lazarus Attorney, Agent, or Firm-Sellers and Brace [57] ABSTRACT width of the tubing and facilitate the packaging of an object therewithin. The apparatus advances the flattened tubing past a source of heat so related to the edge or edges to be bulged as to soften only these edge portions of the tubing thereby relieving internal stresses therein and allowing the same to bulge and take a set in bulged condition as it cools.

3 Claims, 4 Drawing Figures hhhhln cation for United States Letters Patent Ser.

APPARATUS AND METHOD FOR PROCESSING HEAT REACTIVETHERMOPLASTIC TUBING AND Ahighly versatile packaging and protective envelope I material has recently become available in the market place in the form of a fully flattened heat-reactive thermoplastic tubing. This tubing has a thin flexible wall structure impervious to moisture and extremely durable, tough, abrasion resistantand the walls of which are heat fusable to one another or to other thermoplastic material. This tubular material has a highly pronounced shrinkage coefficient when heated to a temperature only slightly above normal room temperature. Accordingly it is adapted to be readily assembled about an object to be packaged or protected following which low heating of the tubing film suffices to activate its shrinkage capabilities. The tubing product is available in a wide range of diameters. By selecting a size most appropriate for a particular object, the object can be easily and quickly inserted into the tubing following which it readily shrinks into snug fitting engagement with the adjacent surfaces of the object. The material readily accommodates'itself to differential shrinking thereby automatically adapting itself to irregularities in the surface of the object.

A serious drawback to the 'use of the tubing referred to above resides in the fact that the heat reactive processing to which the basic material is subjected to impart its shrinkage characteristics provides a tubing product havingits opposed side walls flattened flush against one another. The locke d-in internal stresses associated with its heat-reactive properties are particu-v larly pronounced at the return bends of the flattened tubing makin g it a laborious, time consuming operation to separate the walls at the tubing ends when endeavors ing to telescope it over an item. being enclosed therewithin. Various expedients have been resorted to inef for-ts togain access to the interior of the tubing but, prior to the present invention, these have not been satisfactory or productive. These efforts have included attempts to jet pressurized air into. the ends of the tubes to expand the walls away from one another, and so trimming the end of the tubing as to provide a leading end engagable with the fingernail or some sharp instrument. However, neither these nor other effortshave been successful. s r

By the present invention there is provided simple apparatus and a technique for processing flattened heatreactive tubing to bulge the edge portion just suffi ciently to permit entry of an object and thereby expedite expansion of the remainder of the cross section. This expedient does not interfere withthe compact packagingand storage of the product itself until ready for use, yet provides a continuous shallow passage lengthwise of the product into which the operator's thumbnail or some other object can be inserted and employed to open the remainder of the tubing end. For some purposes, only one edge need be so processed al- 2 though it is found desirable and helpful if both edges are similarlyprocessed.

The material is processed rapidly and uniformly by passing the portion to be expanded. in heating proximity to a heat source effective to heat only a selected portion of the tubing. As the heated portion softens slightly, certain of the internal stresses are relieved and rendered immediately effective to bulge the softened portion. One simple mode. of processing the tubing comprises feeding the flat stock continuously past a source of heat effective to heat only a limited edge area of the tube. Portion so heated-immediately bulges and takes a set while cooling.

Accordingly, it is a primary object of this invention to provide a novel apparatusand an improved technique for processing flattened heat-reactive thermoplastic tubing to cause a selectedportion thereof to bulge and take a setin bulged condition.

Another object of the invention is the provision of a thermoplastic tubing product having a high shrinkage coefficient and having a small passage extendinggenerally lengthwise thereof.

These and other more specific objects will appear upon reading the'following specification and claims andupon considering in connection therewith theattached drawing to which they relate.

Referring now to the drawing in which a preferre embodiment of the invention is illustrated:

FIG. 1 is a generally schematic side elevational view of apparatus suitable for practicing the invention method;

FIG. 2 is a cross sectional view on an enlarged scale 1 taken along line 2-2 on FIG. 1';

FIG. 3 is a fragmentary perspective view of the tubing prior to processing; and

FIG. 4 is a view similar to FIG. 3 but showing the tubing processed to provide a bulge along either lateral Referring initially more particularly to FIGS. 1 and 2, there is shown apparatus, designated generally 10, suitable for practising the invention method. Since the details of the main frame are of no consequence, none is shown but it will be understood this frame includes suitable means for supporting a supply reel 11 holding a quantity 12 of heat-reactive thermoplastic tubing 13 having the initial configuration illustratedin FIG. 3.

It will be understood that tubing 13 is available as a flexible ribbon-like tube the opposite side walls of which are fully flattened against one another while being processed to give it its high heat shrinkage characteristics. Although the tube walls are thin and readily flexible, internal stresses prevail throughout the wall structure including the return bend portions 14. For this reason, it is difficult and vexatious to attempt spreading the walls apart sufficiently to insert an-object. To overcome this shortcoming, tubing 13 is processed according to the present invention by passing it from supply reel 11 through a slot 17, and thence through a processing station designated generally 18.

mating with the threads of an adjusting screw 23. This screw has one end journalled in jaw 19 and the other end journalled in a stationary boss 24 mounted on the machine frame. Hand crank 25 can be rotated to adjust jaw 20 relative to jaw 19 thereby to accommodate the processing of tubing 13 of various widths.

Any simple means may be provided for applying heat to the return bend portions 14 of the flattened tubing.

Such means may comprise hot air supply passages or small electric heaters 26 extending lengthwise of jaws 19, 20 and effective to heat only one or both edges of the tubing as it passes through processing station 18. Only sufficient heat should be supplied to the tubing to soften a narrow band thereof. Such softening enables the internal stresses imposed during the heat reaction processing to become effective to expand the tubing thereby providing one or more long shallow passages 28, 28 having a tear drop shape in cross section. It is unnecessary to supply pressurized air into these passages during heating, the mere heating and partial softening of these edges permitting the softened portions to expand automatically into the configuration shown.

As the tubing passes to the left past processing station 18 it enters between a pair of drive rollers 29, 30 and onto take up reel 31. The latter is preferably power driven in any suitable manner. It will be understood that suitable drag mechanism for supply reel 1 1 may be employed to maintain the tubing under slight tension while being processed.

The completed product may be stored on reels or cut to appropriate length for packaging in straight strip form. In use, the operator inserts his fingernail or a tool 1 carried in or attached to the palm of his hand into one end of passage 28 and employs this entry to expand the tubing as necessary for the insertion of the article being packaged.

While the particular apparatus and method for processing heat-reactive thermoplastic tubing and the product formed thereby herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the detail of construction or design herein shown other than as defined in the appended claims.

I claim: 1. Apparatus for processing a continuous length of thermoplastic tubing obtainable in the marketplace and of the type having a high shrinkage coefflcient effective to shrink the tubing to'a substantially smaller diameter when heated to the point of softening and typically manufactured and marketed with the lateral edges sharply creased and the intervening sidewalls flattened flush against one another and strongly resisting expansion away from one another to permitthe assembly of said tubing over an object and which processing has as its purpose the conversion of at least one sharply creased lateral edge of said fully collapsed tubing and the immediately adjacent portions thereof into a stable small diameter continuous tubular passage to facilitate expansion of the remaining portions of said flattened sidewalls, said apparatus comprising means for supporting a coiled supply of said sharply creased and flattened heat shrinkable thermoplastic tubing, power driven means for passing said tubing from said coiled supply past a heating station, said heating station including means for supporting said collapsed tubing at said heating station with the sidewalls adjacent at least one sharply creased edge of said tubing unobstructed and free to bulge from end to end of said heating station, means supported along the lateral edges of said flattened tubing at said heating station having parallel passages in contact with an adjacent lateral edge of said tubing and in light pressure contact therewith in the plane of said flattened sidewalls, and means at said heating station to heat at least said one sharply creased lateral edge portion sufficiently to soften said edge portion as pressure is applied lightly thereagainst whereby said fully collapsed sidewalls adjacent said one creased edge shringk and bulge to form a stable small diameter continuous passage from end to end of said tubing readily entered from the end to expand said flattened sidewalls away from one another.

2. The apparatus defined in claim 1 characterized in the provision of adjustable means at said heating station to support flattened tubing of different widths.

3. The apparatus as defined in claim 1 characterized in that said heating means is positioned to heat said tubing support means opposite one lateral edge thereof. 

1. Apparatus for processing a continuous length of thermoplastic tubing obtainable in the marketplace and of the type having a high shrinkage coefficient effective to shrink the tubing to a substantially smaller diameter when heated to the point of softening and typically manufactured and marketed with the lateral edges sharply creased and the intervening sidewalls flattened flush against one another and strongly resisting expansion away from one another to permit the assembly of said tubing over an object and which processing has as its purpose the conversion of at least one sharply creased lateral edge of said fully collapsed tubing and the immediately adjacent portions thereof into a stable small diameter continuous tubular passage to facilitate expansion of the remaining portions of said flattened sidewalls, said apparatus comprising means for supporting a coiled supply of said sharply creased and flattened heat shrinkable thermoplastic tubing, power driven means for passing said tubing from said coiled supply past a heating station, said heating station including means for supporting said collapsed tubing at said heating station with the sidewalls adjacent at least one sharply creased edge of said tubing unobstructed and free to bulge from end to end of said heating station, means supported along the lateral edges of said flattened tubing at said heating station having parallel passages in contact with an adjacent lateral edge of said tubing and in light pressure contact therewith in the plane of said flattened sidewalls, and means at said heating station to heat at least said one sharply creased lateral edge portion sufficiently to soften said edge portion as pressure is applied lightly Thereagainst whereby said fully collapsed sidewalls adjacent said one creased edge shringk and bulge to form a stable small diameter continuous passage from end to end of said tubing readily entered from the end to expand said flattened sidewalls away from one another.
 2. The apparatus defined in claim 1 characterized in the provision of adjustable means at said heating station to support flattened tubing of different widths.
 3. The apparatus as defined in claim 1 characterized in that said heating means is positioned to heat said tubing support means opposite one lateral edge thereof. 